When images are upscaled or interlace video images are made progressive, stepwise patterns which are referred to as “jaggies” are produced at edge portions in images. For example, image processing methods of removing these jaggies are variously proposed (see, for example, Patent Literatures 1 and 2).
The image processing methods disclosed in Patent Literatures 1 and 2 include sequentially selecting each pixel of an input image as a pixel of interest. Further, by extracting an area (window) around this pixel of interest and comparing (in other words, pattern matching) the area and a jaggy pattern prepared in advance, whether or not the pixel is a jaggy pixel is decided. When this pixel is a jaggy pixel, a jaggy correction pattern prepared in advance is read, and is added to a portion corresponding to the jaggies of the input image to remove the jaggies.
Further, Patent Literature 3 discloses an image processing device which defines a filter and prevents jaggies. The image processing device disclosed in Patent Literature 3 detects a brightness gradient of a predetermined range around a pixel of interest. Further, the image processing device detects an edge gradient direction v1 which is a direction in which a gradient of a pixel value is the greatest and an edge direction v2 which is a direction which is orthogonal to the edge gradient direction v1 in the pixel of interest. Furthermore, the image processing device detects eigenvalues λ1 and λ2 which each indicate a dispersion of a gradient of each pixel value in the edge gradient direction v1 and the edge direction v2. Still further, the image processing device disclosed in Patent Literature 3 detects reliability of an edge based on λ2/λ1, and generates a parameter p matching the reliability. Further, the parameter q a value of which changes according to a rising of the edge is generated based on a fact that contrast is significant across the edge and the edge is clear when the eigenvalue λ1 is great. Furthermore, the image processing device disclosed in Patent Literature 3 calculates a range of filtering processing based on p and q, switches the number of taps of the filtering processing based on the range and defines a filter.
That is, the image processing device disclosed in Patent Literature 3 defines a filter which prevents jaggies in a predetermined range related to each pixel of interest in an image.